1. Field of the Invention
The present invention is generally directed to a movable feed for use with a stationary toroidal antenna in communication with geosynchronous satellites and more specifically to the arrangement for supporting and moving the feed along the arc of the toroidal antenna as well as perpendicular thereto.
2. Prior Art
The standard method for tracking a synchronous satellite for communication is to use a steerable paraboloidal antenna capable of looking at the total visible sky or a large segment thereof. Since satellites can now be maintained in a position to with .+-.1.degree. and closer it is not necessary to be able to steer the antenna beam for complete or nearly complete sky coverage. The satellites are set in a "parking space" in the sky which span approximately 20.degree. of longitude. In order to steer a conventional antenna the complete structure is driven to maintain a constant optical configuration. Dead load deflections in all elevation angles must be considered to obtain an optimum acceptable surface tolerance. Dual drive motors and gears operating in a manner opposed to each other are required on each axis to steer the antenna accurately and to eliminate steering errors which would result from backlash. The drive and servo-control systems are designed to maintain accurate tracking and pointing to within 0.1 and 0.2 of the antenna beam width. The drives must be capable of driving in high winds so the antenna can be stowed to protect the structure at high survival winds.
In most prior art steerable antenna an extremely powerful drive system must be employed since the weight of the entire structure will range between 30,000 and 1,000,000 pounds depending on the type and the size of antenna used. When a steerable antenna is utilized the feed for the antenna is generally remote from the transmitting and receiving equipment or the transmitting and receiving equipment must be mounted in a moving elevated room on the conventional steerable antenna thereby adding substantially to the weight to be driven.
Furthermore, with some prior art arrangements it was necessary to utilize a separate and independent steerable antenna for communication with each satellite even when two or more synchronous satellites were stationed in the same region or "parking lot".